Bug 77778 - Want CONFIG_SCSI_MULTI_LUN=y for usb mass storage
Want CONFIG_SCSI_MULTI_LUN=y for usb mass storage
Status: CLOSED NOTABUG
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
8.0
All Linux
medium Severity medium
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Assigned To: Arjan van de Ven
http://www.fredshome.org/Linux/UnoMas/
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Depends On:
Blocks:
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Reported: 2002-11-13 10:00 EST by Need Real Name
Modified: 2007-04-18 12:48 EDT (History)
1 user (show)

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Doc Type: Bug Fix
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Last Closed: 2003-03-25 19:16:59 EST
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Description Need Real Name 2002-11-13 10:00:03 EST
From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)

Description of problem:
I wish the kernel were built with:
CONFIG_SCSI_MULTI_LUN=y

This is becoming more important as compact flash, memory stick etc become more 
popular and more users buy USB drives for smart medias.

Because USB media is treated as SCSI and single products often contain many 
devices we need CONFIG_SCSI_MULTI_LUN=y for all devices to be discovered.

Perhaps you know why CONFIG_SCSI_MULTI_LUN=y is a bad idea?  Cos I can't think 
why it should be disabled.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
Follow instructions at http://www.fredshome.org/Linux/UnoMas/

Actual Results:  $ cat /proc/scsi/scsi
Host: scsi0 Channel: 00 Id: 00 Lun: 00  Vendor: OEI-USB  Model: 
MMC/SD           Rev: 1.02  Type:   Direct-Access                    ANSI SCSI 
revision: 02


most devices are not seen.



Expected Results:  $ cat /proc/scsi/scsi
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: OEI-USB  Model: MMC/SD           Rev: 1.02
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 00 Lun: 01
  Vendor: OEI-USB  Model: SmartMedia       Rev: 1.02
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 00 Lun: 02
  Vendor: OEI-USB  Model: CompactFlash     Rev: 1.02
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 00 Lun: 03
  Vendor: OEI-USB  Model: Memory Stick     Rev: 1.02
  Type:   Direct-Access                    ANSI SCSI revision: 02 


All luns detected

Additional info:
Comment 1 Arjan van de Ven 2002-11-13 10:04:54 EST
it is a bad idea because it breaks several scsi devices (mostly scanners)
In addition to that: this is a runtime option!
add
options scsi_mod max_scsi_luns=127
to /etc/modules.conf
Comment 2 Brian Brock 2003-03-25 19:16:59 EST
Explanation seems good, resolving as not a bug.
Comment 3 Stephen Walton 2004-02-28 17:53:56 EST
I know this is ancient history, but I just hit this issue and a minor
comment seems in order.  After adding the "options" line to
/etc/modules.conf, you'll have to rebuild the initrd and reboot for it
to take effect.  Rebooting with the old initrd but with the options
line changed has no effect.
Comment 4 Need Real Name 2004-02-29 03:39:59 EST
This is a very good point you make.

For completeness I record the suggestion that you also need to 
rebuild initrd because the scsi module is loaded from the ramdisk, 
possibly because you boot from scsi disks.

Folk without scsi boot devices who dont load the scsi module from 
initrd won't need to do this.
Comment 5 Jerry Uanino 2005-12-27 10:35:03 EST
Just some additional comments, you can cat commands directly 
to /proc/scsi/scsi and accomplish this without a reboot... if you are just 
using some flash card readers, you can always have those commands cat'd in an 
init script. (see scsi programming howto on ldp for more info).

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